Table 3.

Optical fiber sensors.

Sensor Type	Application	Sensing Element	Key Parameters	Ref.
Textile	HR, RR	Woven hetero-core silica OF	Error 4 bpm, SD of 1% on a full scale of 2.3 dB (0.2 N)	[208]
Chest belt	HR, RR, BP, PWT	400 µm multimode OF	Laboratory testing, HRV 2.5%,	[209]
Sensing head	HR, RR	No-core fiber laser	Shifts of lasing wavelength	[210]
Respiratory mask	RR	SMS fiber structure	Power variations in OF, fast and reliable response, long lifetime	[20]
Skin-like wearable	Motion, pressure	Glass MNF in PDMS layer	bending radius 30 μm, fast response for pressure sensing	[212]
Textile	HR, RR	POF sensor	High dynamic range and sensitivity, Error 4 bpm and 2 rpm	[214]
Chest belt	RR	D-shaped POF sensor	RR under different movement st	[215]
Elastic band	HR, RR	Hybrid plasmonic microfiber knot resonator embedded in PDMS membrane	Planar strain 1 ‰, Sensitivity 0.83 kPa−1, Minimum 30 Pa, Ascending time 20 ms	[216]
Chest belt	RR	POF sensor woven in textile	Error 3 rpm	[217]
Attachment	Join angle detection	POF sensor (3:2 elastomer/gel)	Strain up to 60% (loss of 30 dB)	[218]
Mattress	HR, RR, activity	POF sensor	Error 2 bpm and 1 rpm	[219]
Smart bed	HR, RR	Multimode POF sensor	Comparative between analysis methods (FTT vs Hilbert trans.)	[220]
Cushion	RR	SFS structure Fiberglass mesh/SFS/PVC layer	Error 1 bpm, Enhanced sensitivity	[221]
Bedsheets	Skin perfusion, SpO2, HR, pressure on tissue	POF sensors embroidered into moisture-wicking fabric	Low static friction, Withstands disinfection with hospital-type laundry cycles	[222]
Mattress	RR	4 × 4 matrix structures of POFs embedded in the mattress, Arduino	645 nm and silicon PD, Resolution 2.2–4.5%/N.	[224]
pH sensor	pH	Ratiometric sensor based on hybrid sol-gel pH sensing material deposited on a POF tip	Excellent sensor reproducibility, long-term stability, response time 2 min, drift 0.003 pH (22 h)	[225]
Mattress	HR, RR	Macrobend small core OF	High vibration sensitivity, reliability, and good stability	[227]
Pediatric vital signs	HR, RR	Microbend fiber optic sensor under barrier sheet	Mash structure, monitoring of babies	[226]
Chest belt	RR	SMS microbend fiber structure	Six different SMS fiber sensors were tested on six subjects	[229]
Skin-like wearable	HR, BP	Ultrathin optical sensor based on a self-assembled wavy microfiber combined with ECG	Sensitivity ≈ 257 per unit strain, good repetition (SD 1.7% over 100 cycles)	[19]
Human motion	Motion	Plasmonic gold nanoparticles into stretchable elastomer-based OF with a core/cladding structure with step-index configuration	Strains 100%, Detection limit ±0.09%, Responsivity < 12 ms, Reproducibility over 6000 cycles	[230]
Human motion	Motion	Graphene-coated fiber sensors	High sensitivity, Broad sensing range, High reproducibility	[231]
Vital parameters	BP, BT, RR, HR	FBG twin Fabry–Perot interferometer	Mean values within ±5 mmHg, SD 1 ±8 mmHg	[206]
T-shirts	HR, RR, BP	Single-mode fibers MZI	Inserting discontinuities in OF to break total internal reflection and scatter/collect light	[233]
Chest belt	RR	Single-mode fibers MZI	-	[234]
Mattress	HR, RR	Twin-core fiber-based sensor Sandwich single-mode fiber	Sensitivity 18 nm/m−1	[235,236]
Thin pad	HR, RR, respiration amplitude	MZI inserted between two elastic layers	Errors 2 bpm and 1 rpm, 3 × 3 coupler based differentiate and cross-multiplying method	[237]
Wearable photonic	EMG, ECG, EEG	Lithium Niobate MZI	Wavelength 1530–1565 nm, Gain 1 to 4 mV/μV, Sensitivity 20 μV	[238]
Device	HR	Fabry-Perot interferometer	Strain sensitivity 2.57 pm/μN, Good responses to LF vibrations	[239]
Probe for intravascular sensing	BP, BT	Fiber-optic sensor with a confined air cavity and sub-micron geometric resolution	Resolution 0.11 mmHg (760 to 1060 mmHg) Resolution 0.036 °C (34 to 50 °C)	[240,241]
Smart textile	HR, RR	FBG sensor	Three volunteers, three locations	[246]
Chest belt	RR	FBG sensor	Tested wavelengths 525, 660, 850, 1310, 1550 nm	[18]
Intelligent clothing	BT	FBG sensor	Sensitivity 0.15 nm/°C (33–42 °C), 15x of the bare FBG	[247]
Temperature mapping	Skin temperature 3D mapping	FBG temperature sensors, light source, circulator, fiber coupler	Absolute error 0.11 °C	[248]
T-shirt	HR, RR	Three FBGs glued on the textile with silicone rubber	Highly stretchable and compressible	[249]
Textile	RR	Two FBGs	Sleep apnea, RR during sport	[250]
T-shirt	HR, RR	FBGs	Sensitivity 0.35 nm⋅L−1, RR accuracy 0.045 s, Error 2.7 bpm	[242]
Radial artery sensor	BP, pulse waveform	FBG sensor, interrogator, light source, circulator	Sensitivity 8.236 nm/N	[252,254]
Multichannel hybrid FO	HR, RR, BT	Two FBGs encapsulated inside PDMS	-	[253]
Skin-like	Muscle motions	FBG-based SFO strain sensor	Mold dimension 2 × 10 × 20 mm	[256]
Textile	RR motion pattern	12 FBGs	RR error 0.2 rpm, RV error 0.09 l	[257]
Smart bed	ECG, HR, BP, PPG, BT, Inspired O2	FBG in fabric	Monitoring patient under magnetic resonance imaging	[261]
Smart bed	HR, RR, BT, motion	FBGs in bed	Alert system for residents, Optical network, Error 1 bpm	[193]
Cushion	HR, RR	FBG mounted inside cushion	The error of ±3 bpm and ±1.2 rpm	[262]
Respiratory mask	RR	FBG bonded over a respiratory mask	Remote and continuous RR monitoring	[264]
Multi-parametric	RR, neck movement	Two custom flexible sensors based on FBG technology	-	[267,268]
Nasal flow	RR	FBGs, cantilevers	Nasal airflow into a cantilever	[269]
Wrist-worn device	BT, BP	FBG	Sensitivity 1 pm/mmHg, 0.5 pm/mmHg, 18.9 pm/°C	[272]
Breath humidity monitor	RR relative humidity	Needle, which houses graphene oxide deposited FBG sensor	Response ∼42 m, Sensitivities 18.5 pm/%RH, 0.027 dB/%RH (30∼80%RH)	[274]
Multi-sensor platform	BT, pressure, localization	Lenses at the tip of OF three light sources: 637, 780, 875 nm	BT precision ±0.22 °C, pressure 1 mmHg, localization 3 mm	[275]